Gaia Theory

The crisis of sustainability demands that we think again about the nature of our planet and the biosphere that sustains us. The modern worldview clearly distinguishes between rational, thinking humans and a non-human world devoid of intelligence, determined by “chance and necessity.” But there is another view, Gaia theory, which sees planet Earth as a self-organizing whole, maybe a living being. Gaia theory derives from scientific inquiry into the systemic, interconnected nature of the planet – planetary systems science. It can also be seen symbolically as a rediscovery of anima mundi, the soul of the world. It is “the next big idea”, according to the philosopher Mary Midgley, big enough to reunite science and spirituality, to give us an appreciation of how the Earth and her inhabitants matter for themselves, regardless of any use we humans might wish to put them to.

Gaia theory originates with James Lovelock’s work for NASA in the 1960s. Lovelock – a Fellow of the Royal Society – was then known for his work on instrumentation, for example inventing the electron capture detector, which demonstrated the build up of DDT in the biosphere and of fluorocarbons in the ozone layer. He was employed by NASA to develop equipment to be landed on Mars to detect the existence of life. As he considered this, he realized that one could tell whether there was life on Mars without sending a spaceship there, by looking at the chemical composition of planetary atmosphere. The Martian atmosphere is 95% carbon dioxide; while the Earth’s is 21% oxygen and 77% nitrogen. So the Martian atmosphere is at chemical equilibrium – all possible chemical reactions have occurred; while the Earth’s atmosphere is far from equilibrium with large quantities of oxygen, a highly interactive gas. Something is going on here on Earth other than chemical interaction to hold the atmosphere at this statistically improbable state.

Lovelock concluded that it was the interaction between living things and the earthly environment which not only made Earth’s atmosphere but regulated it, keeping it at a composition favourable for life over billions of years. In the 1960s and 70s this was far from the conventional view. The non-living world of rock, atmosphere and ocean were seen to determine key variables for life. Living things must adapt to these conditions or die. In his book Animate Earth, Lovelock’s colleague Stephan Harding writes

Gaia theory proposes two radical departures from this conventional view. The first is that life profoundly affects the non-living environment, such as the composition of the atmosphere, and this then feeds back to influence the entirety of the living world. Gaia theorists talk about a “tight coupling” between living and non-living worlds. The second proposal is that out of this tight coupling between life and non-life comes an unexpected property – the ability of Gaia, of the Earth system as a whole, to maintain key aspects of global environment, such as global temperature, at levels favourable for life, despite shocks and disturbances from both within and outside itself.

Gaia is a way of describing Earth as an interconnected whole with emergent properties of self-regulation. We can take the long-term carbon cycle as an example. Carbon dioxide pours out of volcanoes; since carbon dioxide is a greenhouse gas, if too much is accumulated the planet will get too hot. The Gaian self-regulating system locks up carbon at such a rate as to maintain temperature within appropriate limits for life. The weathering of granite rock allows calcium ions to escape and combine with rainfall and carbon dioxide in the atmosphere to make calcium bicarbonate. This is washed down to the sea and used by algae called cocolithophores to create their shells, which as they die sink to the seabed forming layers of chalk. So when you see the white cliffs of Dover you are looking at carbon deposits. And, extraordinary though it may seem, when you pick up a piece of granite rock you are holding something which participates directly in the processes of life on Earth. When the planet’s temperature increases, these chemical reactions speed up, so providing a feedback loop to increase the sequestering of carbon dioxide; and as temperature cools, the reactions slow down. But these physical and chemical reactions are insufficient to explain how temperature has stayed at a level suitable for life over eons. Life comes into the picture by increasing the weathering of rock in many ways, so that calcium ions are more available for linking with carbon – roots of trees crack open rock, bacteria secrete compounds and lichens release acids – all of which accelerate chemical weathering, faster at higher temperatures, slower at lower temperatures, providing further self-regulating feedback. Life participates fully in the creation and maintenance of its own environment.

Although an oversimplification, this account is now generally accepted in the scientific community. Earth science research has shown many other ways in which life processes are central to maintaining the steady state of Earth’s temperatures and other essential qualities of the biosphere. Gaia theory shows that there is an intimate and complex connection between life on Earth and the self-regulating properties of Gaia, that the whole planetary system is an intricate, self-sustaining and self-organising web of life.

So what is happening to this web of life, and in particular what is happening to the carbon cycle? We humans – actually, we humans in the industrialized North, but increasingly also those in the fast industrializing countries like China – through burning carbon fuels are releasing carbon which has been locked up for millennia; and there is increasing evidence that intensive agricultural activities in the majority world such as rice paddy fields emit large quantities of greenhouse gases. Simultaneously, we are damaging the planet’s capacity for self-regulation by, for example, cutting down forests. As we pursue our short-term interests we are cutting through self- regulatory cycles and causing an upsurge in planetary temperature with accompanying disturbances to the weather system.